These are taiyaki: not really fish, but fish-shaped, these are a dessert that have been popular in Japan since the the early 1900s. They are essentially filled waffles, with the most common fillings being sweetened azuki beans and custard. Taiyaki translates as baked sea bream; they taste much better than the name sounds.

Other versions of filled waffles are found throughout Asia. The other common shape is a round, hockey-puck shaped cake, such as depicted below in Taichung, Taiwan:

the photo depicts waffles being prepared with taro and sweet potato fillings, both local favorites in Taiwanese desserts, in addition to my favorite, made of crushed peanuts mixed with brown sugar.

Here in the San Francisco Bay Area, we are lucky to be able to find taiyaki fairly easily: May’s Coffee shop in the Japan Center mall in San Francisco’s Japantown sells the traditional version, and a cute little cafe in San Mateo called Sweet Breams makes a miniature version, depicted in the first photo. Besides the common azuki, custard, and chocolate fillings, Sweet Breams serves some interesting other flavors, such as Nutella and eggnog.